This invention relates to fluid circulation devices. More specifically, the present invention relates to devices and methods for improving the efficiency of air fans.
Fluid circulation devices are utilized in a variety of domestic, commercial, and industrial applications. Air circulation devices in the form of fans typically comprise impellers made up of a plurality of blades attached to a hub. In commercial and industrial applications where the operational requirements of the fans are high, the blades are typically made with metal to sustain high speeds over extended periods of use. In these commercial and industrial applications, such as automobile plants, fans may be found in great quantity. Because each individual work station will frequently have its own fan, a single plant may use hundreds or possibly thousands of them.
Because of the high number of the devices that are used in commercial and industrial applications, small gains in efficiency have a measurable impact on the overall cost of operating them even in a single plant. Hence, many attempts have been made to increase performance and efficiency which are measured by several factors: output in cubic feet per minute (cfm), overall power consumption, and heat rise of the device.
Attempts to increase efficiency frequently involve altering the shape of the blade. Past attempts at modifying blade shapes have resulted in complex parabolic or hyperbolic blade configurations and complex variations of the pitch at which the blades attack the surrounding air. However, operational blade shapes are limited because the available processes for forming metal blades are not capable of forming certain blade shapes cost effectively, if at all, and developing the tooling for mass production of a new blade shape is costly.
In attempts to overcome some of the costs of modifying blade shapes, separate components have been attached to the blade in attempts to improve efficiency. These attempts typically involve adding an extension to the trailing edge of a blade thereby increasing its surface area and hopefully the efficiency of the air circulation device. Increases in efficiency gained by these previous blade attachments have been small, unsuited for commercial and industrial applications, and, therefore, of minimal significance.
Thus, improvements in fan efficiency are desirable to enhance air flow and to reduce the cost of operation. It is also desirable to obtain such increases in efficiency without modification of existing blade shapes and means for attaching the blades. Increases in efficiency obtained without modifying the actual blade shape or the means for attaching the blades to hubs, reduce the cost of production for fans.